Fr. Chaminade and the Normal Schools

Brother John Emling, S.M., earned his doctorate in education at Western Reserve University. He also has a background of graduate study in business administration and economics. He is not just a theorist in education, having taught at Duquesne University and St. Mary \u27s College, California, before coming to the University of Dayton

Double-Dipole Excitations in 40Ca

The double-dipole strength distribution in $^{40}$Ca is calculated microscopically within a model space of 1p1h - and 2p2h excitations. Anharmonic effects in the centroid energies of the $0^+$- and $2^+$ components are found to be small, in agreement with experimental observation. Firm conclusions about the spreading width cannot be drawn, as yet, due to computational limitations in the number of 2p2h states.Comment: 8 pages of LaTeX, two figures available at ftp://rsm1.physcis.uiuc.edu/pub/figs

Underwater ambient noise

Underwater sound continues to be a problem of high priority in naval warfare. Since atomic bombing may render obsolete most types of surface ships, the relative if not absolute importance of the submarine certainly has increased. Thus, the U. S. Navy logistics chief recently told a congressional committee, By far the most important and difficult problem which confronts the navy in so far as ship characteristics and fleet operating technique are concemed is the problem of undersea warfare

Equivalence of the long-wavelength approximation and the truncated Taylor expansion in relativistic Coulomb excitation

The long-wavelength approximation and the truncated Taylor expansion are frequently used in the theory of relativistic Coulomb excitation to obtain multipole expansions of the interaction. It is shown in this note that these two approximations are exactly equivalent.Comment: 5 page

Anharmonicities of giant dipole excitations

The role of anharmonic effects on the excitation of the double giant dipole resonance is investigated in a simple macroscopic model.Perturbation theory is used to find energies and wave functions of the anharmonic ascillator.The cross sections for the electromagnetic excitation of the one- and two-phonon giant dipole resonances in energetic heavy-ion collisions are then evaluated through a semiclassical coupled-channel calculation.It is argued that the variations of the strength of the anharmonic potential should be combined with appropriate changes in the oscillator frequency,in order to keep the giant dipole resonance energy consistent with the experimental value.When this is taken into account,the effects of anharmonicities on the double giant dipole resonance excitation probabilities are small and cannot account for the well-known discrepancy between theory and experiment

Boson expansion methods applied to a two-level model in the study of multiple giant resonances

We apply boson expansion methods to an extended Lipkin-Meshkov-Glick model including anharmonicities in analogy with previous microscopic calculations. We study the effects of different approximations present in these calculations, among which the truncation of the hamiltonian and of the space, in connection with the study of the properties of two-phonon and three-phonon states. By comparing the approximate results on the spectrum with the exact ones we conclude that the approximations made in the microscopic calculations on two-phonon states are well justified. We find also that a good agreement with the exact results for the three-phonon state is obtained by using a bosonic hamiltonian truncated at the fourth order. This result makes us confident that such approximation can be used in realistic calculations, thus allowing a theoretical study of triple excitations of giant resonances.Comment: 12 pages, 2 figures, Latex with epsfig.st

Quenching of 1+1^+ excitations in the double giant resonance

The electromagnetic excitation of the two-phonon isovector giant dipole resonance in relativistic projectiles incident on heavy targets can be proceed via several intermediate $1^-$ one-phonon giant resonance states. In two step electric dipole transitions the population of $0^+$, $1^+$, and $2^+$ two-phonon states are possible. We calculate the amplitude distribution of $1^-$ excitations with an RPA formalism, and use it to calculate the electromagnetic excitation of two-phonon states in second order perturbation theory and coupled-channels. We show that a conspiracy between angular momentum coupling and the strength of the electromagnetic fields suppresses contributions of $1^+$ states to the total cross sections.Comment: 10 pages, 2 Postscript figures available upon reques

How harmonic is dipole resonance of metal clusters?

We discuss the degree of anharmonicity of dipole plasmon resonances in metal clusters. We employ the time-dependent variational principle and show that the relative shift of the second phonon scales as $N^{-4/3}$ in energy, $N$ being the number of particles. This scaling property coincides with that for nuclear giant resonances. Contrary to the previous study based on the boson-expansion method, the deviation from the harmonic limit is found to be almost negligible for Na clusters, the result being consistent with the recent experimental observation.Comment: RevTex, 8 page